1. Field of the Invention
The present invention relates to a structure for fixing links and pins of a traveling crawler chain to be used in a crawler-type vehicle. More particularly, it relates to a link-and-pin fixing structure for a crawler chain, which enables the links and the pins to be fixed to each other easily and firmly and in which the links and pins can be assembled securely at a low cost.
2. Description of the Related Art
Plural ground-contact track shoes are mounted to an endless link chain with mounting bolts in a traveling crawler chain of a crawler-type vehicle of construction machine such as a bulldozer or a hydraulic shovel. For assembling this link chain, pins for connecting links, which are press-fitted into cylindrical bushes respectively, are press-fitted into the respective end portions of right and left links successively. The cylindrical bushes have their respective both ends exposed outside. The end portions of the respective links are coupled with each other with pins in an articulated manner such that they are part from each other. The end portion of each link is provided with a lubricant-sealing member and its crush-preventing spacer for preventing internal abrasion between the pin and the bush. Lubricant reserved within the pin is supplied to between the pin and the bush.
Generally, the aforementioned link chain is used for travelling on hard, soft ground composed of soil, sand, gravel or the like or hard, soft slope ground of such. Therefore, the link chain interferes with outside obstacles, rocks or the like. Thus, the respective links tend to receive an external force in their axial direction through a flange or the like of a lower roller of the vehicle. Additionally, end faces of the pins also tend to receive an external force or the like in their axial direction through a roller guard or the like of the vehicle body, so that the pin becomes loose easily. If the pin is held with a small force, it may start or come out. Thus, the lubricant-sealing member and the crush-preventing spacer of the sealing member disposed at the end portions of the links are easily deformed, starts to be displaced or damaged.
If the sealing member or the crush-preventing spacer of the sealing member is damaged, consumption speed of the lubricant is accelerated so that an internal abrasion occurs between the pins and the bushes to damage the pins or bushes. As a result, the function of the link chain is lost in a short period. Thus, the links and the pins are fixed to each other by a strong press-fit in order to prevent the link and the pin from being moved in their axial direction by an external force. Furthermore, there has been employed a mechanism for preventing the pins from coming out of the link.
As this pin-coming-out preventing mechanism, for example, Japanese Patent Application Publication No. 5-79548 discloses a link-and-pin fixing structure.
In this conventional fixing structure, each link is provided with an annular socket having a diameter-expanding slope surface directed outward in the axial direction, at an outside end face of a pin-press-fit hole. An exposed end portion of the pin has an annular groove dented smoothly inward in the axial direction of the link from its end face. Thus, when the pin is pressed into the pin-press-fit hole of each link, there is formed an annular hollow portion having an opening inclined outward between the groove in the pin and the socket of the link.
Then, an annular pressing-in retainer for preventing come-out of the pin, which is made of metallic material, is pressed into the annular hollow portion through its opening between the pin-press-fit hole in the link and the exposed end portion of the pin. The pressing-in retainer is plastically deformed along an inner wall of the hollow portion so that the hollow portion is filled with the retainer. By employing this slip-out preventing mechanism, there is an advantage that a moving of the pin in its axial direction can be suppressed.
Meanwhile, when a joint composed of the link and the pin is repaired, the pin is pushed out from the end portion of each link and the pressing-in retainer is cut out. Then, the cut-out pressing-in retainer is taken out of the hollow portion. Next, an end portion of the pin is press-fitted into the pin-press-fit hole of the link and a new pressing-in retainer is brought into the opening of the hollow portion. Consequently, the hollow portion is filled with the new pressing-in retainer similarly to above.
However, according to the above described Japanese Patent Application Publication No. 5-79548, the annular pressing-in retainer is pressed into the annular hollow portion as being plastically deformed so that the hollow portion is filled with the deformed pressing-in retainer. Thus, the pressing-in retainer needs to be filled securely between a surface of the groove in the pin and an inner face of the socket of the link. That is, if the filled annular pressing-in retainer is not fitted locally between the groove surface of the pin and the inner face of the socket of the link, it is easily peeled off. Consequently, a holding force of the pin in the axial direction is decreased to make the pin loose easily. Thus, durability cannot be expected.
Therefore, a complicated machining, a high dimensional precision and the like are required. Further, it is necessary to adjust positions of the socket of the link and the groove in the pin accurately, which requires more equipment cost, production cost and the like, as well as strict quality control. However, it is impossible to visually check an internal shape of the deformed and filled pressing-in retainer in the hollow portion. Therefore, not only in assembling of the link and the pin, but also in an inspection after the assembling work, it is not possible to see whether or not the deformed pressing-in retainer is fitted securely to the wall of the hollow portion. Thus, quality of products can not be uniform, and defective products are often produced.
The present invention has been accomplished to solve the above-described conventional problems. An object of the present invention is to provide a link-and-pin fixing structure of a crawler chain that makes it possible to fix the link and the pin to each other securely and firmly and secure a holding force for holding the pin sufficiently in its axial direction. Further, the present invention has an object to produce a link-and-pin fixing structure of a crawler chain that allows assembling of the link and the pin to be carried out easily at a low cost.
The above-described object is achieved effectively by following features of the present invention.
Firstly, according to the present invention, there is provided a link-and-pin fixing structure of a crawler chain, wherein a fitting space having an annular opening, in which an elastic ring whose diameter of a section is D is to be fitted, is formed between an opening end portion of a pin-press-fit hole of a link and a press-fit end portion of a pin exposed in the opening end portion; a link inner wall of the fitting space is formed with an tapered inner-diameter face whose diameter gradually decreases as it goes toward an inmost of said fitting space such that the tapered inner-diameter face intersects an axial line of the pin at a predetermined angle xcex1; an outer peripheral face of the exposed end portion of the pin exposed in the fitting space is formed with an tapered outer-diameter face whose diameter gradually decreases as it goes toward the inmost of said fitting space such that the tapered outer-diameter face intersects the axial line of the pin at a predetermined angle xcex2; said tapered inner-diameter face intersects an inner-diameter surface of said pin-press-fit hole at said angle xcex1 via an inner annular face continuous to said tapered inner-diameter face, and said tapered outer-diameter face intersects said inner-diameter surface of said pin-press-fit hole at said angle xcex2 via an outer annular face continuous to said tapered outer-diameter face; and when dimensions of distances between each contact points of the tapered inner-diameter face and the tapered outer-diameter face in the fitting space and a horizontal line passing the center of the section of the elastic ring are d1 and d2 respectively, the dimensions d1 and d2, the diameter D of the section of the elastic ring and the angles xcex1 and xcex2 have a relation as follows; xcex1 greater than xcex2, D greater than d1+d2 (where d1=D/2xc2x7cos xcex1, d2=D/2xc2x7cos xcex2).
That is, according to the present invention, the annular fitting space is formed between an inner face of the opening end portion of the pin-press-fit hole of the link and the exposed end portion of the pin, and the elastic ring having a section of the diameter D can be fitted in this fitting space. An inner wall face of the link in this fitting space has an tapered inner-diameter face whose diameter gradually decreases as it goes toward the inmost of the fitting space such that the tapered face intersects the center of the pin-press-fit hole in the link at the predetermined angle xcex1.
On the other hand, an outer peripheral face of the pin exposed in the fitting space has an tapered outer-diameter face whose diameter gradually increases as it goes toward an opening side of the fitting space such that the tapered face intersects its axis at the predetermined angle xcex2. At a deep position in the fitting space, the tapered outer-diameter face and tapered inner-diameter face intersect each other via the respective annular faces continuous thereto. Such a fitting space is so constructed that the dimension of its opening is larger than the diameter D of the elastic ring""s section and narrowed gradually as it goes from the opening end toward the inmost of the fitting space.
Thus, the elastic ring is fitted to the pin end portion through the opening of the fitting space in a state that it is expanded more than it normally is. Then, while holding the tapered outer-diameter face of the pin elastically, the elastic ring is pressed into the fitting space along the tapered outer-diameter face as it decreases the tightening force gradually.
When the elastic ring is fitted in the fitting space, each of lines (radius of the elastic ring""s section, D/2) connecting the contact positions of the respective tapered faces with the center of the elastic ring""s section forms a predetermined angle with respect to a perpendicular line passing the center of the elastic ring""s section. Each of the angles xcex1 and xcex2 is respectively the same as the angle xcex1 formed by the tapered inner-diameter face of the link and the angle xcex2 formed by the tapered outer-diameter face of the pin as mentioned above.
According to the present invention, the contact point between the elastic ring and the tapered inner-diameter face of the link when the ring is fitted is located within a xc2xc circle in the fourth quadrant of the elastic ring""s section, in order to set up a preferred fixing structure for the link and the pin by the elastic ring. The contact point between the elastic ring and the tapered outer-diameter face is on the other hand located within a xc2xc circle in the second quadrant of the elastic ring""s section. Thus, a preferable fixing structure of the link and the pin with the elastic ring according to the present invention can be set.
Then, the angle xcex1, which is formed by the line (radius (D/2)) passing the contact point between the ring and the tapered inner-diameter face of the link when the elastic ring is fitted and the perpendicular line passing the center of the ring""s section, is set to be larger than the angle xcex2, which is formed by a line (radius (D/2)) passing the contact point of the tapered outer-diameter face of the pin with the ring when the ring is fitted and the center of the elastic ring""s section and the perpendicular line passing the center of the ring. Further, according to the present invention, the diameter D of the elastic ring""s section is set to be larger than a sum of d1 and d2, which are dimensions from the respective contact points between the elastic ring and the respective tapered faces to the horizontal line passing the center of the elastic ring""s section.
According to the present invention, with the above described structure, the elastic ring is brought into the fitting space along the tapered outer-diameter face of the pin while decreasing the tightening force of the ring such that the ring contacts with the outer and inner tapered faces in the fitting space at the respective predetermined positions. Thus, the elastic ring can be fitted easily between the respective tapered faces by a relatively small pressing force.
If the elastic ring is pressed between the respective tapered faces, the respective tapered faces are given with a force pressing the elastic ring toward the inmost of the fitting space based on the tightening force of the elastic ring. Thus, even if a fitted posture of the elastic ring in the fitting space is varied, the posture of the elastic ring is corrected in the fitting space so that the elastic ring can be fitted and fixe therein firmly.
If an external force in the axial direction is applied to the link or the pin, a force directed in an opposite direction along the tapered face is applied to a contact position between the tapered face and the elastic ring. At the same time, the tightening force of the elastic ring acts on the tapered outer-diameter face. The direction of the tightening force at this time is vertical to the tapered outer-diameter face. Therefore, the force directed toward the inmost of the fitting space along the tapered outer-diameter face is a sum of a component force of the external force along the tapered outer-diameter face and a component force of the tightening force of the elastic ring along the tapered outer-diameter face.
On the other hand, as described above, the elastic ring keeps contacting with the respective tapered faces in the fitting space with a relation of xcex1 greater than xcex2 with respect to the perpendicular line passing the center of its section. Thus, the component force directed toward an entrance of the fitting space along the tapered inner-diameter face of the link based on the aforementioned external force is smaller than the sum of the aforementioned component forces applied along the tapered outer-diameter face.
Consequently, even if an external force in the axial direction is applied to the link or the pin, the elastic ring is always pressed toward the inmost of the fitting space, so that the elastic ring never comes out of the fitting space. Further, even if the external force in the axial direction increase, the aforementioned component force generated along the tapered outer-diameter face of the pin also increases. Consequently, a large force to press the elastic ring toward the inmost of the fitting space is applied, so that the elastic ring is urged to go deeper in the fitting space by itself. Consequently, the elastic ring is retained more firmly in the fitting space.
That is, according to the present invention, when the external force in the axial direction is applied to the link or the pin, the force for pressing the elastic ring deeper in the fitting space is always larger than the force for pressing it out. Thus, the fitting force of the elastic ring is automatically intensified, so that the moving of the link or the pin in the axial direction can be prevented securely, whereby no looseness occurs. Thus, even if an impact in the axial direction is applied to the link or the pin, deformation, damage or the like of a lubricant-sealing member and its crush-preventing spacer disposed in a joint portion of the respective links can be prevented so that sufficient durability of the link chain is secured.
Further, according to the present invention, there is provided a typical structure that can achieve the same effects as mentioned above only by placing the elastic ring into the fitting space.
Specifically, there is provided a link-and-pin fixing structure for a traveling crawler chain, in addition to the above-described structure, wherein a contact position of the elastic ring with said tapered outer-diameter face in said fitting space when said elastic ring is fitted therein is located within a region of said tapered outer-diameter face extended in the axial direction.
With such a structure, only by placing the elastic ring into the region of the tapered outer-diameter face of the pin in the fitting space, the elastic ring contacts thereto in the fitting space with an appropriate tightening force. Therefore, further to the aforementioned effects of the present invention, the elastic ring can be fixed easily and firmly between the respective tapered faces in the fitting space.
Furthermore, according to the present invention, it is preferable that said elastic ring is a C-shaped ring made of an annular metallic material whose part is cut out and having an inside diameter smaller than a diameter of a narrowed portion of said press-fit end portion of the pin.
That is, the inside diameter of the elastic ring is set to be smaller than the outside diameter of the tapered outer-diameter face of the pin in the fitting space. Thus, if the elastic ring is fitted in the fitting space, a force directed toward the inmost of the fitting space is applied to the elastic ring by the tightening force of the elastic ring. Consequently, only by placing the elastic ring into the fitting space, the elastic ring can be set easily at an appropriate position that contacts with the tapered inner-diameter face of the link and the tapered outer-diameter face of the pin.
Still further, according to the present invention, it is preferable that of the respective annular faces continuous to said tapered outer-diameter face and said tapered inner-diameter face, at least the outer annular face continuous to the tapered outer-diameter face is curved in the axial direction so as to be dented.
If a switching portion between the tapered outer-diameter face and the outer annular face is formed linearly at a predetermined angle, there is a possibility that a crack or the like occur at the switching portion when an external shock is applied thereto after the pins and links are fixed to the elastic ring. According to the present invention, because the switching portion is formed in a curved face so as to be dented, any possible occurrence of the crack or the like can be avoided. Furthermore, when the elastic ring is fitted in the fitting space, the ring face-contacts with part of the outer annular face curved to be dented. Thus, the fitting position of the elastic ring can be fixed. Consequently, in addition to the aforementioned function according to the present invention, a stabilized fixing function for the pin and link can be exerted.